The invention pertains to a rotary vane vacuum pump with a high vacuum stage, with a fore-vacuum stage, with a substantially cylindrical rotor which has bearing and anchor segments, a bearing segment being situated between two anchor segments and the anchor segments having vane slots, and with a roughly pot-shaped housing which contains the pump chambers and whose base is designed as a bearing piece with a passage for the rotor drive.
High vacuum pumps require that the individual parts which effect the pumping of the gas be manufactured with the utmost precision. If, for example, in the case of a rotary vane vacuum pump, the slots between the vanes and the related vane slots in the rotor, the slots in the area of the anchor systems, or in the case of a two-stage rotary vane pump--the slots in the sealing area between the high vacuum stage and the fore-vacuum stage are too large, then flows occur which oppose the intended direction of flow (backstreaming) and which significantly impair the pumping characteristics, pumping speed, compression, ultimate pressure characteristic etc.
From FIG. 3 of DE-A-2354039 a two stage rotary vane vacuum pump of the aforementioned kind is known. Besides the bearing segment being situated between two anchor segments, the rotor has on one of its two face sides, (on the side of the fore-vacuum stage) a further bearing segment. Both vane slots must therefore be milled from the direction of the other face side--(the high vacuum side)--into the rotor. This has the disadvantage that a milling disc having a relatively large radius, greater than the sum of the lengths of the two vanes and the length of the bearing segment in the middle, must be employed. Moreover, after milling of the vane slots and for the purpose of manufacturing an operational rotor, a filling piece must be inserted again at the level of the middle bearing segment, so that a leak-tight mutual separation between the two stages of the vacuum pump is ensured. The manufacture of a rotor of this kind is involved. Milling of the vane slots is only possible with limited tolerances owing to the necessity of having to employ a milling disc of a relatively large diameter.